Fig. 1.

The vicious cycle of chronic catecholamine stimulation in heart failure. With an acute event and a healthy heart, βAR activation by catecholamines increases cardiac output without deleterious effects (within limits). With prolonged stimulation of a failing heart, which has less capacity to respond, continued forced contractility has extensive maladaptive consequences leading to worsening cardiac output. The cycle can be attenuated by β-blockers or GRK activity. See Introduction for discussion.